Re: [PATCH] Introduce array_shuffle() and array_sample()

Martin Kalcher <martin.kalcher@aboutsource.net> writes:
> If we go with (1) array_shuffle() and array_sample() should shuffle each 
> element individually and always return a one-dimensional array.

>    select array_shuffle('{{1,2},{3,4},{5,6}}');
>    -----------
>     {1,4,3,5,6,2}

>    select array_sample('{{1,2},{3,4},{5,6}}', 3);
>    ----------
>     {1,4,3}

Independently of the dimensionality question --- I'd imagined that
array_sample would select a random subset of the array elements
but keep their order intact.  If you want the behavior shown
above, you can do array_shuffle(array_sample(...)).  But if we
randomize it, and that's not what the user wanted, she has no
recourse.

Now, if you're convinced that the set of people wanting
sampling-without-shuffling is the empty set, then making everybody
else call two functions is a loser.  But I'm not convinced.
At the least, I'd like to see the argument made why nobody
would want that.

            regards, tom lane